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1989 740 GLE 16 valve starts but wont run 700

I recently got myself a 1989 740 GLE 16 valve sedan (LH2.4). According to the previous owner, it had a fuel delivery problem, it wouldn't start. So the first couple of things I checked was of course the fuel pumps, and relay. I swapped out the relay, and put it in my other 740, and that car fired right up, and still runs with that relay 2 weeks later. So then I checked the pumps, and with direct 12 volts to them, they run fine. I also checked the radio suppression relay, I did the same thing as with the fuel pump relay, swapped it with the one in my other 740, and it was fine. I also pulled the harness off the AMM, to see if it would go into limp home mode, but no difference. The only way that I have been able to start it is by jumping the feed from te fuel pump relay that is supposed to feed power to the fuel pumps (pink wire #87/2 on the relay), and plugging that wire into a 12 volt source, then the pumps run, and when I turn the key it fires for a second, and then dies right away. All the fuses are good, all grounds that I have checked are good, I have good spark, it just wont run. What could it be that I am missing?? Any leads or input would be greatly appreciated, thanks!!!









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740 GLE 16 valve starts but wont run 700 1989

Are your spark plugs wet or dry after cranking? If dry, consider checking the Radio Supressor Relay (which has nothing to do with the radio but simply provides power to the fuel injectors). This relay is the same as your electric fan relay (if you have one) and both of them are mounted in the engine bay (black relay boxes, usually with 4-pin plugs on the bottom).

Also, if the diaphram in the Fuel Pressure Regulator has ruptured, the engine will be flooded and the mixture will be too rich to start. The last ruptured regulator that I had allowed the car to cough for a moment, but promptly flooded it. Supsequent cranking seemed like a no-spark issue, except that there was spark and the plugs were wet. -just a bit too wet.

Take a look through the brickboard no-start/hot-start FAQ since there's a lot of good information in there that will help you along.

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 231K








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1989 740 GLE 16 valve starts but wont run 700

if you always nhave spark, try this. on the fuel pump relay, there is a ground feed from the ecu. when the car comes on. the fuel pumps prime, you start and the ecu supplies the ground to keep the relay closed while starting. if this ground is missing, you need an ecu. be advised 16v ecus do not interchange with any other 700s. good luck, chuck.








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1989 740 GLE 16 valve starts but wont run 700

It kinda sounds like the Cold Start injector is working during start-up (which would cause the car to run far a second or two), but the regular injectors aren't.

89's had some bad ECU's. Is there enough compatibility between your two cars that you could swap in your other ECU?

Have you read out the fault codes?








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1989 740 GLE 16 valve starts but wont run 700

I haven't had a chance to check the fault codes. I have been looking for a reference on the codes so I know what they are. Unfortunately my other car is an '88 740 turbo, and it has the earlier LH2.2, so the ECU's aren't compatible. Anybody have a good reference on where to get the fault codes? Which port do I plug it in to again? Also, the ignition needs to be on when I read the codes, right? Could the crank speed sensor have anything to do with it? Is there a way to check if the ECU is good? Or is that something a dealer has to do?

Thanks!








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1989 740 GLE 16 valve starts but wont run 700

How to extract and clear Fault Codes (from 700/900 FAQ's):

http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

If you're getting spark the whole time, it would seem to the crank sensor would be OK. One of the faults codes should point to that if it's a problem.








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1989 740 GLE 16 valve starts but wont run 700

Is there a way to test the ECU? Or do I need to bring it to a dealer for that?








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1989 740 GLE 16 valve starts but wont run 700

Try swapping the fuel pressure regulator between the cars, and see if that helps. 10 min job. Round thingy at the front end of fuel rail. Might save you some. My Haynes manual has pretty OK description of error codes and procedure, although if I remember right the codes are divided between two separate places in the manual, one for ignition etc, one place for the rest. Write down what error codes are stored and remeber that some of them might be old. Then erase, and try restarting. Then test again for error codes. This/these new ones should be most relevant.







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